The present invention generally relates to semiconductor devices and methods of producing the same, and more particularly to a semiconductor device having a radiator structure and to a method of producing such a semiconductor device.
Recently, due to the improved integration density of semiconductor devices, the amount of heat generated by the semiconductor device has increased. Hence, there are semiconductor devices having a radiator structure for releasing the heat generated from the semiconductor device. It is desirable that the semiconductor device having such a radiator structure be produced with ease and with high dimensional accuracy.
FIG. 1 shows an example of a conventional semiconductor device having a radiator structure. In a semiconductor device 1A shown in FIG. 1, a radiator block 3 having a flange 3a is provided at a central opening part of inner leads 2a of a lead frame 2. The radiator block 3 has an inverted trapezoidal cross section. Ends of the inner leads 2a and the flange 3a of the radiator block 3 are fixed by calking at a calked part 4.
A semiconductor chip 5 is mounted on the radiator block 3 by soldering or the like, and this semiconductor chip 5 is bonded to the inner leads 2a by wires 6. In other words, a die-bonding is made using one surface of the radiator block 3 as a stage. The semiconductor chip 5, the inner leads 2a and the like are encapsulated by a resin which is molded to form a package 7, and outer leads 2b are thereafter bent in an approximate S-shape or a gull-wing shape to suit the semiconductor device 1A for surface mounting.
The radiator block 3 is mounted on the inner leads 2a at the calked part 4. Hence, the thickness of the lead frame 2 must be 300 to 400 .mu.m at the minimum in order to enable the calking. In other words, because the radiator block 3 is fixed to the lead frame 2, it is necessary to make the calking which limits the thickness of the lead frame 2. Furthermore, in order to enable the calking, the radiator block 3 must be made of a metal.
On the other hand, when injecting the resin into a metal die so as to mold the resin and form the package 7, the accuracy of the position of the exposed surface of the radiator block 3 becomes poor depending on the injection pressure. That is, it is difficult to control the position of the exposed surface of the radiator block 3. In addition, resin burr or flash occurs if the position of the exposed surface of the radiator block 3 changes. The resin burr or flash may deteriorate the thermal conduction efficiency of the radiator block 3 when the semiconductor device 1A is mounted on a circuit substrate (not shown) or the like. Furthermore, if resin burr or flash exists, the adhesion of the radiator block 3 to the circuit substrate via an adhesive agent becomes poor when the semiconductor device 1A is mounted on the circuit substrate, because the adhesive agent used would naturally have good adhesion to the metal forming the radiator block 3 and not to the resin forming the resin. burr or flash.
Moreover, when producing the semiconductor device 1A, the relatively heavy radiator block 3 which is made of a metal must hang from the lead frame 2 when molding the resin to form the package 7. However, the lead frame 2 is thin as described above to enable the calking, and it is difficult to stably support the radiator block 3 in the correct position during the molding process, and unwanted bends may be formed in the lead frame 2.